Research ArticleAPPLIED SCIENCES AND ENGINEERING

Soft electromagnetic actuators

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Science Advances  26 Jun 2020:
Vol. 6, no. 26, eabc0251
DOI: 10.1126/sciadv.abc0251
  • Fig. 1 Working principle and fabrication process of SEMAs.

    (A) Schematic working principle of a SEMA subjected to a current load in a magnetic field. (B) A swimming soft shark driven by SEMAs (tail and fins; movie S1). (C) Main steps of the SEMA fabrication: molding of the silicone elastomer, bonding to a sheet of elastomer to fabricate channels, and, last, injection of the liquid metal. Front and side layout of the finished square SEMA with both ends of the liquid metal connected to a control system. (Photo Credit: Michael Drack and Guoyong Mao/Johannes Kepler University Linz).

  • Fig. 2 Characterization of a single-coil square SEMA.

    Rotation angle of the SEMA subjected to a DC current from 1 to 3 A (A) predicted in the simulation and (B) observed experimentally (movie S3). (C) Rotation angle of the SEMA as a function of the current for experiment and simulation. (D) Temporal change of the surface temperature of the SEMA for three specific values of DC current, 1, 2, and 3 A. (E) Maximum rotation angle of the bending SEMA subjected to square wave currents, with varying amplitude and frequency. Inset: Maximum rotation angle is limited by the actuator touching the ground. (F) Fatigue test with 5 Hz at a current of 1 A. Comparison of the voltage drop versus time at the beginning and the end of the test shows a perfect overlap of the first and the 2.16Mth bending cycle, evidencing the high durability of the SEMA. (Photo Credit: Michael Drack and Guoyong Mao/Johannes Kepler University Linz).

  • Fig. 3 Power and efficiency of a double-coil square SEMA.

    (A) Experimental setup for the power and efficiency test. By switching the DC current from −3 to 3 A, the SEMA bends from one to the other side and lifts the weight by 2 cm via a deflection pulley (movie S5). (B) Displacement of the SEMA responding to the sudden current change from −3 to 3 A. (C and D) The velocity and mechanical power response of the SEMA over time in the initial 0.2 s after switching the current. (E) A double-coil square SEMA hits a ping-pong ball mounted on a string 47 mm into the air (movie S6). (Photo Credit: Michael Drack and Guoyong Mao/Johannes Kepler University Linz).

  • Fig. 4 Functionalities of SEMAs.

    (A) Dynamic swinging of a fish-tail SEMA (top view; movie S7). (B) Fish-tail SEMA as a blender speeding up the mixing of blue dye and water (movie S7). (C) Flower SEMA (top view). The five petals are numbered from 1 to 5. The elastomer support joining the five SEMAs to one flower is described in fig. S11B. (D) Flower SEMA in different actuated modes (movie S8). Each bit of the binary number represents the on- (1) or off-state (0) of a single petal corresponding to the numbers in (C). (E) Design and operation of a cubic SEMA and its rotation subjected to different current signals (movie S9). (Photo Credit: Michael Drack and Guoyong Mao/Johannes Kepler University Linz).

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